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Agriculture, the world’s oldest and most important industry, has in comparatively recent years been revolutionized by the application of ingenious machinery to its many operations, which include ploughing, sowing, harvesting and threshing


COMBINED HARVESTER AND THRESHER at work on a farm at Elmscott, Suffolk. This machine cuts and threshes corn in one operation. With two men working the machine it will cut and thresh forty acres of corn in one day. Without the machine it would take fifteen men several days merely to cut and bundle the corn obtained from the same area.

MANY people, in answer to the question, “What is the world’s leading industry?” suggest transport or textiles, shipping or coalmining. The most important industry in the world, however, is agriculture. For thousands of years man’s brain has helped his hands to overcome the hardship of his toil in the fields, by enlisting the machine to subdue the soil.

The perfecting of the agricultural machine has become an important branch of engineering and in many of the universities of the world the subject is being intensively studied. There is, for instance, in the University of Oxford a flourishing Institute for Research in Agricultural Engineering.

Probably the oldest known agricultural implement is the plough. Its utility has been increased a hundredfold; oxen have given place in turn to horses, to steam engines and finally to the powerful paraffin-driven and diesel-driven tractors of to-day. The

first plough was possibly the branch of a tree that merely scratched the surface of the land.

Thousands of years have evolved the modern steel plough capable of turning many furrows at one time. The single-furrow plough, drawn by a team of horses, may he regarded as the forerunner of the multi-furrow ploughs that are hauled by tractor. The action of the plough is similar whether drawn by horse or by mechanical power.

The horse-drawn implement used for ploughing furrows comprises a beam to which the other components are attached. At the front is the clevis, to which the hauling chains are attached. Alterations to the hitch, or position of the chains, vary the depth and width of the furrows. Behind the clevis are two wheels placed side by side. One runs on the unploughed land, the other in the furrow. The next component on the beam is the coulter, which cuts the ground vertically, and behind this is the body or frame of the plough. The body carries the ploughshare, which cuts the furrow slice horizontally, and immediately behind is the plough breast, which turns the slice over. Attached to the left-hand side of the plough body is the landside, a long plate extending backwards from the ploughshare, and its function is to keep the plough straight by bearing against the furrow wall. The body rests on another plate called the slade, or sole, which slides along the ground. Finally there are the stilts, or handles by which the plough is guided.

When a tractor is used for ploughing, a number of plough beams are “ganged” together in a strong framework carried at the front end by land and furrow wheels, and supported by an additional wheel at the back. The clevis of the horse plough gives place to a special hitch capable of adjustment while the tractor is in motion. An interesting feature of the tractor-drawn gang plough is the provision of a wooden peg in the hauling gear. Should the plough strike against a large stone or tree stump, the peg breaks and the implement is thus saved from damage. Tractor ploughs are provided with self-acting gear which allows for the lifting of the cutting portions of the implement above ground level.

The size and shape of the ploughshare vary according to the type of work to be undertaken. For use in stony ground the ploughshare is narrow and pointed; for digging, where the slice is completely inverted, a broad-bladed share is used. Ridging, that is the throwing up of land into ridges, as for potato growing, requires a double-breasted plough with a sharp point.

The coulter, which makes a vertical cut in the ground in advance of the ploughshare, may be a knife or a revolving steel disk fitted with a scraper or skimmer to keep it free from soil. In some ploughs the whole of the digging portion comprises a large concave disk of steel set at an angle to the beam.

Many special-purpose ploughs have been produced from time to time, and one of these is the “skim” plough, used for cutting off stubble and weeds about two inches below the surface. This type of plough is generally drawn by a tractor and comprises a framework carried on four wheels. The ploughshares,- numbering three or four, are in the form of double-edged horizontal blades that can be lifted above ground after use.

Another type of implement that meets special requirements is the one-way plough which can turn a furrow right or left and is generally horse-drawn or hauled to and fro across a field by cable. Since the coming of the tractor, about 1914, cable ploughing has not been so general. The steel cable hauling the plough is wound in by a steam-driven drum carried by a traction engine. Two engines are used, one on either side of the field.

ATWO FURROWS AT ONCE are cut by the type of plough shown in these illustrations type of plough in common use for tractor and cable work is the “balanced” machine, with the cutting implements duplicated at either end. The cutting portions face in opposite directions and are used alternately at either end of the furrows.

TWO FURROWS AT ONCE are cut by the type of plough shown in these illustrations. The plough is hauled by a crawler tractor of 30 horse-power. The horse-drawn plough comprises a beam to which the other components are attached. When a tractor is used for ploughing, two or more plough beams are “ganged” together in a strong framework carried at the front end by land and furrow wheels, and supported at the back by an additional wheel. In place of the clevis - the iron to which, in a horse-drawn plough, the hauling chains are attached - there is a special hitch capable of adjustment while the tractor is in motion.

For breaking up the soil below its usual limits of cultivation the “sub-soiler” is used. The subsoiler resembles the ordinary plough in general construction, but the front wheels, are of equal size and the deep plough body carries a narrow pointed share. The subsoil plough works in the furrows left by an ordinary plough and breaks up the earth without bringing any of it to the surface.

Apart from agriculture the plough plays an important part in the essential process of draining the land. The drainage excavator comprises a beam that carries a scoop-shaped ploughshare. In front of the share is an adjustable foot which regulates the depth of cut. Behind the share is a long sloping chain elevator worked by a wheel, and this carries earth away from the cutting edge and deposits it on either side of the trench.

A plough of this type, drawn by a tractor, will cut a trench 7 in. wide and 3 feet deep without difficulty in heavy soil. A trench of these dimensions would be used for the laying of drain or water pipes, but wider trenches can be cut in similar fashion and used as open ditches or drains.

Another implement used for drainage work is the “mole” plough, which comprises a cable or tractor-drawn framework carrying a massive knife-edge coulter. At the lower end of the coulter is the “mole plug”, a sharpened steel cylinder with a diameter of between 2 in. and 3 in. This cuts a tube below the surface of the ground. It has been found that drains cut in this manner, about 18 in. below ground, remain open often for fifteen to twenty years.

The plough, despite its wonderful development during centuries of time, is now supplemented and sometimes displaced by other ingenious implements which till the soil mechanically. These additional aids to farming are termed cultivators, harrows, rollers or rotary tillers, according to modification in their design.

A cultivator bears some resemblance to a large rake, carried on a wheeled framework and equipped with large forward-curving teeth or tines. There are generally two or three separate rows of tines, with six or more in each row, and a selflift gear permits adjustment for depth of cultivation. The tines may be rigidly attached to the frame or arranged on pivots with springs that keep the working teeth against the ground.

Types of Harrow

When the plough and the cultivator have performed their allotted tasks on the land, any remaining clods of earth are finally broken up by one of the farmer’s most useful machines, the harrow. One of the best types of these is the disk harrow, which comprises a massive framework carried on two axles set at an angle to each other. On the axles are placed a series of revolving steel disks, with a diameter of from 16 in. to 20 in. They are generally “dished” and the convex faces are set towards the centre of the axle. The sets of harrows are duplicated in tractor-drawn machines and the leading disks are put on their axles with convex faces in the reverse direction to that of those behind. The disks are provided with scrapers to keep them free of soil.

Some types of harrow resemble cultivators and are fitted with strong spring tines that curve forward as they meet the ground. The tines revolve on a shaft as the harrow is drawn forward and so dig into the earth and break up the lumps comprising the furrows. Other harrows consist of a framework on the underside of which is fixed a large number of steel spikes. One interesting make of harrow is provided with a series of curved knives fitted to a plain transverse framework without wheels but equipped with a driving seat. Each knife or coulter has two curves in its length, one to the right, the other to the left. When the harrow is drawn across the field the clods are cut through and the earth is turned over from side to side by the knives.

The roller follows the harrow for the purpose of compacting the earth for seed sowing, especially on grassland. Rollers may be of the plain cylindrical type, resembling those used in gardens. Cylindrical rollers for farm work are large and heavy implements necessitating the use of a horse team or a tractor. For clod crushing the plain cylindrical roller gives place to the ribbed type, comprising a large number of narrow sections with Y-shaped treads. Rollers of this kind are often made in three sections so that the two outer components can be swung behind the middle roller when passing through farm gates. In the field the roller is used as one long unit.


SECTIONAL VIEW OF A THRESHING MACHINE. Used generally in the farmyard, the thresher has its machinery contained in a rectangular box carried on four wheels for transport purposes. Driving power comes from an independent source. In this type of thresher corn is fed in a conveyer under cutting knives (left) and passes between a bladed drum and what is known as a concave. This is a curved grating of iron wire, through which the grain, with the chaff, falls on to an inclined reciprocating screen. The straw passes through a series of risers which toss it up and drop it on to a reciprocating floor. A rotary blower, seen between the wheels, creates the air blast which blows away the chaff.

There is one type of cultivator that may be said to usurp some of the functions of the plough. This implement is the rotary tiller. Hitched behind a tractor, it is driven by transmission gearing from the tractor engine. The cutting device consists of a shaft on which are mounted a number of curved tines. As the shaft revolves the earth is broken up and flung out behind the machine to form a seed bed.

When the ground has been prepared by one or more of the machines described above, another type of machine is used to sow the seeds for growing the crop it is intended to raise. Through the ages it had been the custom to sow the seed by scattering it from a hand basket, but early in the eighteenth century Jethro Tull invented the first machine sower, or seed drill, as it is called.

The seed drill may be regarded as the first of the “complicated” machines used in agriculture. The modern drill is highly efficient and ensures economy by the placing of seeds at regular intervals, a great improvement over the old haphazard method of broadcasting by hand. The rate and depth of sowing are under the control of the operator.

The seed drill comprises a wide steel framework carried on two large but narrow tyred wheels. At the back of the frame is a long wooden box or hopper which holds the seed; below this are a dozen or more pipes leading down to the furrow openers. Steel disks are generally used to make the narrow furrows for reception of the seed. The disks are free to revolve and are arranged singly or in pairs. Held down by independent springs, they are capable of simultaneous adjustment for depth.

Seed “Boots”

The disks are provided with scrapers, and behind them are the “boots” that drop the seed in the prepared furrows. Behind the boots are short pieces of looped chain which partly cover in the furrows, leaving the finishing process to a harrow. The harrow is sometimes hitched on behind the seed drill.

The seeding mechanism that supplies the seed boots from the hopper is one of the most ingenious devices invented by the agricultural engineer. In each of the pipe openings, or seed runs, in the bottom of the hopper, is placed a feed shell, a dished and grooved disk of metal that divides the opening into two parts. The edges of the feed shells point in a fore-and-aft direction and all are mounted on a common spindle driven by the carrying wheels of the machine. The wheels transmit the drive through a ratchet mechanism that enables either wheel to act independently of the other, or to be reversed without moving the seeding gear.

Interposed between the carrying wheels and the seed-shell shaft is a variable toothed gear that permits alteration in the speed at which the seeds are delivered. This apparatus is fitted with a pointer indicating the correct setting for peas, oats, barley or wheat in any desired number of bushels of seed to an acre.

PREPARING THE GROUND FOR SOWING with a form of rotary tiller Seed cannot escape from the hopper unless the grooved seed shells are in motion. When the disk coulters are lifted, as in turning at either end of the field, the seed gear is automatically cut out. On some types of disk drills the seed shell gives place to a revolving fluted barrel that can be covered at will by a sliding tube. The exposure of more area of each barrel, by the withdrawal of the sliding tube, increases the rate of seed supply without the necessity for a change-speed device, as in the machines fitted with the grooved disk shells.

PREPARING THE GROUND FOR SOWING with a form of rotary tiller known as a “Gyrotiller”. Equipped with a searchlight for night work, this machine can prepare twenty-six acres in twenty-four hours. It can be adjusted to till to depths ranging from 4 in. to 2 feet. The “Gyrotiller’’ illustrated weighs 15½ tons and has an engine of 170 horse-power. The cutting device of a rotary tiller comprises a shaft having numerous curved tines.

A machine that somewhat resembles the seed drill is the distributor used for scattering artificial manure. In this instance a hopper holds the supply of manure, which is delivered by a plain roller and variable slot at the bottom of the container. Other manure distributors rely on a horizontal endless chain, equipped with fingers that draw material from the interior of the hopper and deliver it through a slot in the back. Another type of distributor uses an upper spiked drum, also driven by the carrying wheels, which picks up manure from the hopper and delivers it through a vertical slot behind the machine. The bottom of the hopper in this instance is raised by a rack and pinion gear to maintain a constant supply of material to the spiked drum. In addition to these machines there are many equipped with conveyer belts and screw distributor gear for the spreading of other forms of manure.

Potato growing has evolved a number of highly interesting machines. Although seed potatoes can be planted and covered by the use of the ridging plough, special machines devised for the purpose are much more efficient.

The potato planter generally comprises one or more double-breasted ploughs carried on a wheeled framework. Behind the ploughs are large steel disks, arranged in pairs. These cover in the seed potatoes as they are planted. The seed potatoes are carried in a series of hoppers, from which they are fed to delivery pipes by bucket elevators that are driven from the wheels of the machine.

The harvesting or digging of potatoes is also done by machinery. There are two main types of potato digger, the rotary and the elevator. The rotary digger comprises a framework carrying a large flat share which cuts into the potato ridges. The machine is carried on two wheels that run between the potato rows. The wheels drive a shaft running from front to back of the machine and on the end of this is a “spinner”, fitted with a number of radial arms carrying forks. As the machine is drawn along, this forked propeller revolves and digs out the potatoes, which are then gathered by hand. Sometimes the forks are feathered in the manner of a ship’s paddle wheel, in which instance they enter the ground vertically and thus have a better digging action.

The elevator type of potato digger is a four-wheeled machine, behind whose share is an open elevator rising above the rear wheels. Potatoes and some of the soil are forced up the elevator. During this process most of the soil drops back to the ground. The potatoes are delivered to a shaker, operated by the rear wheels, where they are finally freed from soil and vegetation. Potatoes are graded by a revolving drum covered with sections of wire mesh in various sizes.

Sugar beet is gathered by special machines that pull the roots from the ground, and the modern turnip-lifting machine is designed so that it not only gathers the crop, but also cuts off the tops and tails of the roots as well.

Modern Grass Cutters

Hay making in modern conditions can be carried out almost entirely by machinery. The grass cutter is reminiscent of Queen Boadicea’s chariot, but the axle scythes have given place to a mechanically operated toothed knife carried at one side. The knife, really a series of triangular knives on a common blade, slides from side to side on a cutter bar fitted with fingers that project forward.

The reciprocating action of the knife is derived from a crank, operated through gearing by the wheels. The cutting is done scissors-fashion by the forward edges of the knife teeth as they slide to and fro in slots in the fingers. The cutter bar is pivoted at its point of attachment to the machine so that it can be lifted up for turning or to accommodate undulations in the land. The outer end of the cutter bar is provided with a divider guard and grass board to separate the standing grass from that already cut, which is laid over in a swath.

FOR RAISING RIDGES attachments can be fitted to the GyrotillerThe swaths of grass are turned over for curing in the sun by a special machine equipped with revolving forks somewhat similar to those used in a rotary potato digger. The forks of the swath turner, however, are more of the nature of rakes with long prongs. The rakes are attached to a pair of large disks, one at either end of the machine; they are driven by the wheels.

FOR RAISING RIDGES, as is necessary in potato planting, attachments can be fitted to the “Gyrotiller”. The curved blades of the two disks situated behind the 80 horse-power tractor raise the earth, and the attachments guide it into ridges.

For gathering up the hay before stacking, various kinds of machines have been devised. The simplest of these is the familiar horse-drawn rake, comprising a wheeled framework carrying a large number of long curved teeth or prongs pointing in a forward direction. As the machine is drawn forward the prongs pick up the hay; when sufficient hay has been gathered to fill the rake the prongs are lifted simultaneously by a lever and the hay is left in a heap for loading on to a cart. Frequently, however, the whole process of hay gathering is done by machinery. If the hay is to be stacked outside the field where it is grown, a hay loader is used, hitched behind a motor lorry, a horse or tractor-drawn hay cart. In general appearance the hay loader resembles the escapes used by fire brigades. A high steel frame, carried on a pair of large wheels at the back and on smaller swivelling wheels at the front, supports an inclined elevator. On the rear axle is mounted a toothed gathering drum that revolves with the wheels, picks up the hay and deposits it on the “apron” of the elevator. The apron, built of wooden slats and cord, is carried on two chains that pass round the gathering drum and a pair of pulleys at the top of the elevator. When the hay has been carried up the elevator by the movement of the apron it falls into the wagon below.

Where it is desired to stack hay in its own field a sweep is used to gather the crop and deposit the swaths at the foot of the stack. The hay sweep resembles the horse-drawn rake, but the curved teeth end in a long crossbar and serve only to retain the hay. The lifting of the swaths is done by a series of long poles or teeth that project forward from the machine and are shod so that they do not dig into the ground. When the sweep is full the operator lifts the teeth by a control wheel, and the machine is pushed to the stack site and then backed away, leaving the hay ready for loading on to the stack. Completion of the stack is carried out by an elevator similar to that of the hay loader, but in this instance the machine does not travel forward and the apron is driven by a separate steam or internal combustion engine.

Harvesting Machinery

Many people will remember the sweet-smelling hayfields on which the mown grass was left to dry in the sun, that is, when there was any sun. Efforts are now being made to eliminate this uncertainty and artificial hay drying machines may be found here and there in the country, particularly in the wetter regions.

It is in the harvesting of wheat and similar crops that agricultural machinery takes its most fascinating form. In the grain belts of Russia, in Canada, in the United States and in the wheat lands of South America giant machines gather in the harvest. Drawn sometimes by multiple teams of horses, by motor tractor or by powerful steam engines, the harvesters will attack a vast field of standing wheat and leave behind an acreage of stubble - and thousands of bushels of grain tied up in sacks. In less spacious lands the processes of cutting the crop and separating the grain from the straw are done in different machines, but the principles on which they work remain substantially unaltered.

The combined reaper and binder, used for cutting corn and binding it into sheaves in fields of moderate size, consists of a steel framework carried on two wheels. The larger or main wheel is of steel with a wide ribbed tyre to ensure a good grip on the ground. This wheel carries most of the weight of the machine and drives the various working parts through a system of gearing.


THRESHING MACHINE, of the type similar to that shown in the sectional view shown above. Corn is fed into the machine at one end and at the other end graded grain falls down separate pipes to be delivered into sacks below the openings. The tall stacker or elevator delivers ‘‘tailings” to the drum at the front of the machine for re-threshing.

Extending to one side of the main wheel is a platform which lies parallel with and close to the ground. Along the leading edge of the platform is a mechanical knife functioning in the same way as that used on a grass-cutting machine. On the outer side of the platform is the smaller of the carrying wheels, both of which are adjustable so that the knife can be set to any desired height above the ground. The standing crop is gathered against the knife by a revolving reel that resembles the paddle wheel of an old-time steamship. This reel is driven by the main wheel through gearing and can be moved up or down, backwards or forwards by the operator to pick up corn that lies away from the knife.

The cut corn falls on to the platform, which comprises an endless canvas belt passing over rollers rotated by the main drive of the machine. After having left the platform, the corn passes to the elevator; this consists of two moving canvas belts carried on mechanically-operated rollers. The corn is gripped between the two moving belts of the elevator and carried upwards to the deck of the machine.

Having reached the deck, the com is gathered into sheaves of requisite size and a complicated mechanism, fed from a reel of twine, ties them securely. In some machines the sheaves are ejected immediately they have been bound, ready for stacking and collection. Other machines are equipped with platforms that carry enough sheaves to make a “shock”, ready for carting to the threshing machine.

The operations just described are those on a farm of moderate size, having separate machines for reaping and threshing.

The threshing machine, a familiar sight in the farmyard, consists of a large rectangular box carried on four wheels for transport purposes. Inside the box is a complicated array of machinery driven by an independent source of power, generally a steam engine or a specially adapted tractor. The most important component of the threshing machine is the revolving drum, with its surrounding “concave”, which correspond respectively to the ancient flail and threshing floor. The drum is placed high up in the box, near one end, and consists of a number of large disks on a steel spindle which takes the main drive from the traction engine or other source of power. Fixed round the disks are numbers of grooved beater plates running parallel with the spindle.

Winnowing by Rotary Blower

Round the lower half of the drum is the concave, a curved grating made of iron wire. Corn is fed into the top of the machine over the drum, and the grain is beaten out by the drum plates against the concave grating. The straw passes out from the concave to a long box at the top of the machine. The box is fitted with a mechanically reciprocating floor that works the straw along to the end of the machine, where it is trussed up into bundles for ready removal.

The grain, with the chaff, falls through the concave on to an inclined reciprocating screen. This screen also permits the grain to fall through, but the cavings (or husks) are retained and delivered at the end of the box. The grain passing through this screen falls on to a second receiving board that passes it to a sieve, where a blast of air blows away the chaff.

The air blast is generated by a rotary blower, the modern counterpart of a winnowing fan The grain has now reached a form of sump at the bottom of the machine and from there it is raised by a bucket elevator resembling a dredger.

The elevator delivers the grain to a device known as an awner or hummeller, resembling a large mincing machine. The revolving knives and rubbers of the hummeller polish and clean the grain, which then passes to a second sieve. Here another air blast is used to blow away any remaining chaff. Finally, the clean grain is graded in a revolving wire-mesh drum, and the different sizes are allowed to fall down separate pipes to sacks below the openings.

Machinery is not yet to be found on all farms. There is still some prejudice against mechanization, for several reasons. One of these reasons, as a speaker at the Oxford Conference on Mechanization in Mixed Farming, in 1936, put it, is that, when mechanization is adopted, “there are no promising young tractors running in the pastures waiting to be broken in”.

SIX-CYLINDER CRAWLER TRACTOR designed for hauling agricultural machinery

SIX-CYLINDER CRAWLER TRACTOR specially designed for hauling agricultural machinery in hilly and difficult country. The tractor has a maximum engine horse-power of 52; there are five forward speeds and one reverse. The overall length of the tractor is 11 ft. 9 in.

[From part 22, published 27 July 1937]

You can read more on the “Agricultural Tractor”, “How Grain Cargoes are Handled” and “Milling of Flour” on this website.

Power and the Plough